In addition to their original function of generating a damping force, strut-type shock absorbers in the suspension system of a vehicle also play a role as a structural member positioning the vehicle wheels as a component in the suspension member.
FIG. 16 shows a prior-art example of a strut-type shock absorber 1. The outer side of this shock absorber 1 is provided with an outer shell unit 10 storing a damping force generating mechanism. The outer shell unit 10 is provided with a cylindrical outer shell 3, a spring guide 6 mounted by welding onto the outer shell 3 and supporting a suspension spring and a knuckle bracket 7 mounted by welding on the outer shell 3 and connected to a knuckle.
The knuckle bracket 7 is fixed by welding after press-fitting onto the outer shell 3. The upper and lower ends 7e, 7f of a single-plate type of knuckle bracket 7 are respectively fixed to the outer shell 3 by welding.
Inlays 32, 37 are formed by a mechanical process on both ends of the outer shell 3. A rod guide 9 is mounted on the upper end of the inlay 32. A lower cap 27 is mounted on the lower end of the inlay 37 (see FIG. 19). The outer peripheral section of the lower cap 27 is welded to the lower end of the outer shell 3 together with the lower end 7f of the knuckle bracket 7 and the bottom of the outer shell 3 is sealed.
As shown in FIGS. 17(a) and (b), the outer shell 3 is rotated about the substantially perpendicular center axis O when welding the upper end 7e of the knuckle bracket 7 to the outer shell 3. A flat welding technique is employed in which the torch 61 of the arc-welding unit is oriented downwardly towards the corner between the outer peripheral face 3a of the outer shell 3 and the upper end 7e of the knuckle bracket 7. The shape of the welded section is in the form of a lap weld with a partial fillet weld.
As shown in FIGS. 18(a) and (b), when welding the lower end 7f of the knuckle bracket 7 and the lower cap 27 across the entire periphery of the outer shell 3, the outer shell 3 is rotated about the center axis O which is inclined through an angle of 60 degrees with respect to the horizontal plane. A flat welding technique is employed in which the torch 61 of the arc-welding unit is oriented downwards towards the corner between the lower end 3b of the outer shell 3, the lower end 7f of the knuckle bracket 7 and the lower cap 27. The shape of the welded section has a specific shape comprising a characteristic flare, a lap weld and a partial fillet weld. Consequently highly accurate welding techniques and considerable welding time is required.
As shown in FIGS. 18(b), (c), the lower end 6a of the spring guide 6 is welded simultaneously with the above at three positions to the outer peripheral face 3a of the outer shell 3. The shape of this welded section is in the form of a lap weld.
The assembly line process for the outer shell 3 comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)}{circle around (6)}{circle around (7)} as shown in FIG. 19 and FIG. 20.
{circle around (1)} A pipe member is cut through in order to form a work 41 comprising a right circular cylinder.
{circle around (2)} A drawing operation is performed along the work 41 in order to form a narrow radius section 38.
{circle around (3)} A drawing operation is performed on the lower end of the work 41 in order to form a narrow radius section 39.
{circle around (4)} A cutting operation is performed on the inner periphery of the lower end of the work 41 in order to form an inlay 37.
{circle around (5)} A cutting operation is performed on the inner periphery of the upper end of the work 41 in order to form an inlay 32. A rod guide 9 is engaged to the inlay 32 in a separate step.
{circle around (6)} The work 41 is cleaned with a flushing operation.
{circle around (7)} The lower cap 27 is press fitted to the inlay 37 of the work 41 and fixed by a caulking operation.
The above steps are all automatically performed in a single production line.
The welding line for the outer shell unit 10 comprises the steps in {circle around (1)}{circle around (2)}{circle around (3)}{circle around (4)}{circle around (5)}{circle around (6)}{circle around (7)}{circle around (8)} as shown in FIG. 20.
{circle around (1)} A number or identification sign of the component is stamped on the work 41.
{circle around (2)} The knuckle bracket 7 is press fitted to the outer shell 3.
{circle around (3)} The upper end 7e of the knuckle bracket 7 is welded to the outer shell 3.
{circle around (4)} The lower end 7f of the knuckle bracket 7 and the lower end 6a of the spring guide 6 are welded at the same time to the outer shell 3. The upper end 7e of the knuckle bracket 7 and the lower end 6a of the spring guide 6 are welded at the same time to the outer shell 3.
{circle around (5)} A leakage test is performed in order to confirm the sealing characteristics of the bottom of the outer shell 3 and the work 41 is cleaned as above.
{circle around (6)} A drilling operation is performed on each bolt hole 7c, 7d in the knuckle bracket 7.
{circle around (7)} The width between respective flanges 7b and the knuckle bracket 7 is corrected.
{circle around (8)} A hose bracket is welded to the outer shell 3.
The above steps are all automatically performed in two production lines.